It is known in filleting fish to regain meat parts, which remain on the sceleton and cannot be gained directly with the fillets in such a manner that the skeleton after filleting of the fish are subjected to a press passing process. In this way a product is obtained which contains, besides fish albumen, strips of the black skin of the abdominal cavity, parts of the air-bladder, and the remaining contents of the abdominal cavity, also blood particles which together cause a discoloration of the product excluding the use as human nourishment.